Class Overview

A better implementation of image spans that also supports centering images against the text.
In order to migrate from ImageSpan, replace new ImageSpan(drawable, alignment) with
new BetterImageSpan(drawable, BetterImageSpan.normalizeAlignment(alignment)).
There are 2 main differences between BetterImageSpan and ImageSpan:
1. Pass in ALIGN_CENTER to center images against the text.
2. ALIGN_BOTTOM no longer unnecessarily increases the size of the text:
DynamicDrawableSpan (ImageSpan's parent) adjusts sizes as if alignment was ALIGN_BASELINE
which can lead to unnecessary whitespace.